1. Field of the Invention
The present invention relates to motor vehicle headlights in general, and more particularly to such incorporating tubular light sources, especially gas discharge tubes.
2. Description of the Related Art
There are already known various constructions of motor vehicle headlights, among them such which incorporate tubular light sources, especially gas discharge tubes. Each of these headlights or headlight assemblies includes a reflector that is positioned along the tubular light source and incompletely embraces the same to leave an open end toward and through which it reflects the light emanating from the light source and impinging on the reflector. A light-guiding disk or plate spans the open end of the reflector and directs the light emanating from the light source and reflected by the reflector to a predetermined area situated in front of the vehicle on which the headlight assembly is mounted when in use.
In this scenario, it is known to configure the reflector as a cross-sectionally parabolic cylinder constituted by two parabolic branches or regions that are displaced parallel to the longitudinal direction of the reflector. Such cross-sectionally parabolic cylindrical reflectors reflect the light rays emanating from the tubular light source onto them in directions parallel to respective optical planes of such reflectors. Cross-sectionally parabolic cylindrical reflectors of this kind have a multitude of optical axes that are situated next to each other and extend in parallelism with one another, lying in or actually defining the optical plane. In addition, each of such reflectors has a multitude of foci that are disposed next to each other on a focal axis of the reflector.
However, such a cross-sectionally parabolic cylindrical reflector does not embrace or envelop the tubular source to any great extent in that it exhibits a relatively small embracing angle in comparison to the overall size of the reflector. As a consequence of this relatively small extent of the embracing angle, the proportion of the light emitted by the light source that impinges upon and is thus captured by the reflector and reflected by the same is also relatively small. For this reason, these conventional headlight or similar illuminating units with cross-sectionally parabolic cylindrical configurations are capable of issuing only light beams with a relatively low light intensity and/or density and are not suited for applications in which high light density is called for (for instance, in use as a brake light).
In an attempt to solve this relatively low illumination capability problem, it has been proposed in the past to provide the headlight assemblies with larger-dimensioned reflectors of the conventional type. When this measure is resorted to, it is namely possible to increase the aforementioned embracing angle and thus to capture and reflect a greater proportion of the light rays emanating from the light source. Yet, experience has shown that this approach may lead to other problems, especially those stemming from the amount of space occupied on the motor vehicle by such headlight assemblies, especially since, driven by aerodynamic and/or aesthetic considerations, less and less space is being made available on motor vehicles for the accommodation of headlight assemblies. The end result is that a conflict exists between the quest for the highest possible illumination light intensity, on the one hand, and for the smallest possible headlight dimensions, on the other hand.